Observation of Modulated Structure in High Nb-containing TiAl Alloy by Synchrotron Radiation and Electron Microscopy

Author(s)

J. Sun

On-Site Speaker (Planned)

J. Sun

Abstract Scope

High Nb-containing TiAl Alloys with modulated structure have been exhibited a promising combination of room temperature ductility and creep resistance. The orthorhombic phase has been identified as one of the constituents of modulated lamellae, nevertheless there is no general consensus on its crystalline structure (B19/O phase) and formation paths. In this work, a high Nb-containing TiAl Alloy with composition of Ti-45Al-8.5Nb (at.%) has been prepared and then subjected to aging at temperatures from 823 to 923 K. The microstructure has been investigated by synchrotron radiation X-ray and electron microscopy. The results have shown that the orthorhombic phase within modulated lamellae is O phase rather than B19, which precipitates from the parent α2 phase during aging. The O phase can be considered as further ternary ordering of the α2 phase, which is consistent with theoretical prediction of phase transformation based on a subgroup relation between phases in TiAl-Nb alloys.

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